RFR: 8224214: [AIX] Remove support for legacy xlc compiler

[Baesken, Matthias]

Hello, please review the following change .
For OpenJDK 13 we've moved to XLC 16 as required compiler.
However  we have still   a lot of workarounds and checks in the codebase for the older xlc  compilers.
This changes removes such changes .

Additionally  it  adjusts   the compiler version check in  hotspot/share/utilities/globalDefinitions_xlc.hpp
and 2 typos in os_aix  are fixed .


When  8224214   was created a while ago ,  it was discussed on the mailing list :

"we still set some '-qlanglvl' options for C++ which aren't supported by the new compiler [xlc16/xlclang++] either" .
Those options  generated lots of warnings ,   so they  were removed  already   so  no need to remove them  in  this change .

(  In jdk11  which is built  with xlc12   they can still be found :
flags-cflags.m4:540: -qalias=noansi -qstrict -qtls=default -qlanglvl=c99vla \
flags-cflags.m4:541: -qlanglvl=noredefmac -qnortti -qnoeh -qignerrno"
)


Bug/webrev :

https://bugs.openjdk.java.net/browse/JDK-8224214

http://cr.openjdk.java.net/~mbaesken/webrevs/8224214.0/


Thanks, Matthias